1. Field of the Invention
The present invention relates to an apparatus and a method for charging powder by utilizing frictional electrification. Also, the present invention relates to a powder coating apparatus, and a method of using such a powder charging apparatus in such a powder coating apparatus.
2. Description of the Related Art
An electrostatic power coating method is one for coating charged powder onto the surface of an article to be coated by electrostatic forces. In general, a corona electrification or a frictional electrification is utilized in a method for charging the powder. The corona electrification is excellent in controllability of an electrification rate and an electrification charge amount. Accordingly, a large charge amount can be given to the powder for a short period of time. However, it requires a high voltage and suffers from a problem that the apparatus therefor becomes large and expensive. On the other hand, since the frictional electrification is based upon a contact electrification, it does not require an electric power source. Accordingly, the powder may be charged in a less expensive manner and in a safe manner with a simple apparatus.
However, the frictional electrification suffers from a problem that the charging rate is low and it takes a long time to obtain a predetermined charge amount.